Data mining has received a great deal of attention as a technique for extracting knowledge or information from a large scale data, e.g., a group of SNS messages or content. To protect implicit privacy data in the large scale database against the data mining, methods for uniformly prohibiting public accesses to the data or uniformly encrypting the data have been provided. However, these methods do not satisfy demands of users to share the SNS messages or content that they themselves have posted on their SNS pages.